Phthalates, chemicals found in hundreds of household products, are believed to play a role in the development of uterine fibroids: non-cancerous tumors that form in or near the uterus, which can be the size of a seed like of a soccer ball. These fibroids affect millions of women and can cause pelvic pain or back pain, heavy blood loss during menstruation, painful sexual intercourse or risk of infertility.
These phthalates, known to scientists to interfere with hormones, have been the subject of health studies for about ten years. A number of them have linked exposure to these chemicals to a higher risk of developing fibroids. During the’analysis of five studies in 2017, Chinese researchers have found that women whose urine contains increasing amounts of one of the substitutes for DEHP, a phthalate often added to plastic to make it more flexible, have a higher risk of developing a fibroid. During a 2019 preliminary studyAmi Zota, an environmental health scientist now practicing at Columbia University’s Mailman School of Public Health, and his team found that in African-American women who had surgery for fibroids, those with high concentration of phthalates in their urine (especially DEHP substitutes) had larger fibroids as well as an enlarged uterus.
It is estimated that in the United States, 26 million women between the ages of 15 and 50 have uterine fibroids, and that more than half of them will experience the debilitating symptoms that result. There is currently no treatment capable of permanently reducing the size of tumors. They can resolve on their own, especially after menopause, and the few treatments available are only prescribed if the symptoms become too much to manage.
If some treatments manage to alleviate the symptoms, surgery remains the only option when the drugs prove ineffective or the patient is unable to get pregnant. Women prone to large fibroids may opt for myomectomy, a minimally invasive operation that preserves the uterus. However, in the most serious cases, they may have to undergo a hysterectomy, which is the removal of the uterus.
Although uterine fibroids are very common, we understand them very little, says Zota.
Scientists don’t know what causes these tumors to grow, although genetic mutations, an imbalance of sex hormones and risk factors such as age, ethnicity, obesity and synthetic compounds have often been pointed out. finger. A recent study found that exposing fibroid cells to metabolized DEHP substitutes stimulated their growth in the laboratory and delayed their death. “Phthalates are not said to cause tumours,” said study gynecologist Serdar Bulun of Northwestern University’s Feinberg School of Medicine. “However, phthalates are said to help tumors grow. His team has identified a molecular pathway that promotes the survival and growth of these tumor cells, strong evidence of the link between exposure to phthalates and the development of fibroids.
This study reinforces the link between phthalates and this disease which remains largely underestimated, explains Tracey Woodruff, a scientist at the University of California, San Francisco, who studies the impact of environmental contaminants on reproductive health, and who n was not involved in Bulun’s study.
According to Zota, however, phthalates are poorly regulated, and almost impossible to avoid.
HOW DO PHTALATES ENTER THE BODY?
Qualified as ” everywhere chemicals (“ubiquitous chemicals”) in English-speaking countries, phthalates are a family of man-made chemicals often used as plasticizers to add softness, flexibility and durability to certain materials, such as polyvinyl chloride, or PVC (one of the most widely used plastics in the world), and synthetic rubber. They are present in many household products, such as food packaging, shower curtains, building materials and car interiors. Phthalates are also used as solvents in some cosmetics and other personal care products, as well as in film-coating or coating of certain pharmaceutical tablets and dietary supplements.
Chemicals can be released from these products and enter the food, air or water with which they come into contact. We can therefore swallow, inhale or in turn absorb these phthalate particles through the digestive or cutaneous route. The body then metabolizes these chemicals, producing substitutes that numerous studies were able to detect in human urine, breast milk, and even in blood.
While the U.S. Environmental Protection Agency often uses animal studies to define what levels of exposure are safe for us, studies suggest that some phthalates may have adverse effects on human health, including at levels lower than those officially established. For example, low exposure to phthalates such as DEHP, DBP, BBP and DIBP during pregnancy has been associated with neurological disorders in children, including delayed cognitive development and memory loss. A link between these chemicals and certain malformations of the male reproductive organs in babies could also be observed.
(Read: How harmful are microplastics to our health?)
THE ACTION OF PHTHALATES ON UTERINE FIBROIDS
In laboratory experiments, scientists found that exposure to DEHP allowed fibroid cells found in urine and cultured in petri dishes to to live longer and of multiply more.
It is also known that many fibromatous cells contain mutations in the gene MED12 potentially triggering tumor formation. According to Bulun, the mutation can occur in a single stem cell, which can then divide repeatedly and thus form an entire tumor. DEHP can accentuate this process.
In November 2022 study, Bulun and colleagues demonstrated how mono(2-ethyl-5-hydroxyhexyl)phthalate, a major substitute for DEHP, affected tumor cells. Scientists often study such substitutes because the body quickly breaks down the parent compound to which the individual may have been exposed, forming metabolites which are then released in the urine. The team discovered that this molecule helps tumor cells absorb an amino acid, tryptophan, which is then converted into kynurenine, a compound that activates the aryl hydrocarbon receptor (AhR), known to trigger cancer. This active receptor promotes the growth of fibromatous cells and, at the same time, accelerates the growth of tumors.
“We think that if we can target and interrupt the conversion of tryptophan to kynurenine, then we can stop or prevent the activation of the AhR receptor, which could stabilize tumors and even cause them to resorb,” says Bulun.
LIVING WITH UTERINE FIBROIDS
While living with uterine fibroids can be physically painful, having a hysterectomy is especially stressful for women who want to get pregnant, says Saudia Davis, a 46-year-old from Chicago.
In August 2021, her fibroids had grown very quickly, and her belly had swollen. “It looked like I was four to seven months pregnant,” she explains. The tumors caused her severe pain in her left buttock and she suffered from incontinence whenever she sneezed or coughed. Ms. Davis had a hysterectomy this year. “I had to make up my mind that I could never carry a child by myself,” she confides. “My fibroids were so big and embedded in the uterus that they had to be removed. »
Neither she nor her doctors know why she developed these tumors, or what caused them to suddenly grow. Studies show that, compared to white women, black women, like Ms. Davis, are two to three times more likely to develop fibroids ; their tumors are also larger and more numerous. Their symptoms are therefore more severe, and they are logically more likely to have a hysterectomy. It remains to determine the role of ethnicity in this phenomenon.
Ms Davis wonders if her fibroids might be from the hair care she used for years until she was 42 to straighten her curly hair. These products sometimes contain phthalates and their use could potentially be linked to uterine fibroids.
However, it is difficult to establish a causal link, according to Kyungho Choi, a health-environment scientist at Seoul National University in South Korea. It takes hours for phthalates to enter our bodies, and levels can fluctuate orders of magnitude each day, he explains. Exposure levels should be determined at the onset of illness, but this is almost impossible to do in real life.
We can’t change our age, gender or genetics “but we can reduce the amount of chemicals we use,” he says. “Their role may be minor, but it’s something we have some control over. »